1. Field of the Invention
The invention generally relates to the field of flat vacuum chambers constituting display screens, and more particularly to microtip chambers and plasma screens. More specifically, the invention relates to a method for manufacturing flat vacuum chambers without pumping stem, and the products obtained using this method.
2. Discussion of the Related Art
Such screens are generally constituted by a vacuum chamber made from two thin glass plates, in which a vacuum is generated by pumping through a pumping stem.
These screens are usually manufactured by conventionally depositing onto two glass plates the various elements constituting the cathode and the anode; assembling the two plates so as to face each other in their respective definitive position, with interposition of a sealing fusible joint at their periphery to form a vacuum chamber; generating a vacuum and maintaining it in the chamber while the latter is heated for degassing the components.
The last phase requires the provision, on one of the plates, of an exhaust tube, or pumping stem, to which an exhaust pipe is connected. When the vacuum conditions required for the application are satisfied (generation of a vacuum as satisfactory as possible in the case of microtips tubes, introduction of a gas in the case of plasma screens), the pumping stem is closed, generally by fusion, but an external protuberance still remains, which increases the thickness of the manufactured device. In addition, the pumping stem renders the plate on which it is positioned more fragile, and the plate requires special manufacturing, which increases the manufacturing cost. Moreover, particular care is required to handle and to store the plate and the screen. This technique requires two separate steps for manufacturing each screen, namely: pumping and closing the pumping stem.